1. Field of the Invention
The present invention relates to a checker head and a method of manufacturing the checker head.
2. Discussion of the Background
One example of a conventional checker head is shown in FIG. 9. A checker head 70 shown in FIG. 9 has a structure wherein a lot of arrangement of a contact pin 71, a push spring 72, a pull spring 73 and a conductive wire 74 being disposed in a straight line are penetrated through four bakelite boards 81-84 laminated. Of course a penetration hole to pass the contact pin 71 and so forth is made for each Bakelite board 81-84. And the contact pin 71 has a nail-shape, and whereof edge protrudes from the Bakelite board 81 of the front. In addition, the penetration hole of the bakelite board 81 has a diameter smaller than that of a bakelite board 82, and then the protrusion of the contact pin 71 is regulated by a brim part of the contact pin 71 being contact with a step part of them.
The conductive wire 74 connected with a circuit tester is inserted into the inside of the pull spring 73, and is soldered as shown in FIG. 10. The push spring 72 is assembled in a compressed state in a checker head 70, and pushes the contact pin 71 toward the upper part and the pull spring 73 toward the lower part in FIG. 9. By the pushing pressure of the push spring 72, a contact pin 71 and the pull spring 73 (besides, the conductive wire 74) are connected electrically. In particular, when the tip of the contact pin 71 is pushed to a test pad 97 of a printed circuit 96 that is an inspected object, the pushing presser is increased, and then the electrical connection becomes more certain as the push spring 72 is compressed more. In this state, an electricity signal (a voltage or a current) can is put to the test pad 97 from the circuit tester, or an electricity signal of the test pad 97 (the same) can be detected with the circuit tester.
However, above described conventional checker head 70 includes the following problems. In the first, an assembling operation of the pull spring 73 and the conductive wire 74 (FIG. 10) and a soldering operation are included in its manufacturing process. These operations are inefficient remarkably because of being done in manual operations. In addition, they are easy to make a mistake, and then the yield is low. In the second, the conductive wire 74 must be a material that can be pushed into the pull spring 73. Because of this, a large conductive wire cannot be used, so that a large current cannot be coped with. In the third, the pushing presser of each contact pin 71 against the test pad 97 is easy to become nonuniform. The reason is because a foreign material is easy to come into when the pull spring 73 is assembled in the Bakelite board 83 in the manufacturing process, and then the spring pressure becomes nonuniform. In the fourth, because there are two kinds of springs, and besides, four pieces of Bakelite boards are used, the parts count is too many, and the burden of the manufacturing control is too big.
According to one aspect of the present invention, a checker head includes a front plate, a rear plate, an intermediate plate, an electro-conductive contact pin, a conductive wire and an electro-conductive spring. A front through hole is formed in the front plate which has a front surface configured to face an object to be inspected. A rear through hole is formed in the rear plate to correspond to the front through hole of the front plate. An intermediate through hole is formed in the intermediate plate to correspond to the front and rear through holes. The intermediate plate is sandwiched between the front plate and the rear plate. The electro-conductive contact pin has a front tip part and a rear brim part which has a diameter larger than that of the front through hole. The front tip part protrudes from the front surface of the front plate and is configured to contact the object to be inspected. The contact pin is positioned such that the rear brim part is located in the intermediate through hole. The conductive wire is inserted into the rear through hole of the rear plate and bonded to the rear plate. The clectro-conductive spring is provided in the intermediate through hole between the conductive wire and the rear brim part of the contact pin in a compressed state. The spring electrically connects the contact pin and the conductive wire. One end of the conductive wire which contacts the spring and a front surface of the rear plate which faces the an intermediate plate are on a same plane.
According to another aspect of the present invention, a method of manufacturing a checker head includes inserting a conductive wire in a rear through hole of a rear plate (Process 1). The conductive wire and the rear plate are bonded together (Process 2). A portion of the conductive wire protruding from a front surface of the rear plate which faces an intermediate plate is removed (Process 3). A spring is inserted in an intermediate through hole of the intermediate plate. An electro-conductive contact pin is inserted in a front through hole of a front plate from a rear surface of the front plate facing the intermediate plate such that a front tip part of the contact pin protrudes from a front surface of the front plate. The rear plate, the intermediate plate and the front plate are connected to sandwich the intermediate plate between the front and rear plates and to compress the spring between the conductive wire and the contact pin.